The DDBTRCC Imaging Core B is designed to provide multiple tj^jes of cutting edge fluorescence microscopy and electron microscopy (EM) techniques to study the physiology ofepithelial cells at the level of organs, tissues, cell models, and sub-cellular organelles to our Research Base investigators. These include confocal and multiphoton confocal microscopy with applications for intracellular pH and Ca measurements at a single cell level, FRET microscopy for detection of protein-protein interactions in in vitro and in vivo models, FRAP microscopy for monitoring the changes in protein mobility due to the changes in protein complexes, and META spectral imaging for more than 4 fluorophores. Each microscope is equipped with temperature controlled perfusion chambers either for tissue or for cell culture studies. The Core also offers ratio-excitation imaging systems of single cells (microscope/camera based) or groups of cells (fluorometer) for quantitative measurements of ion concentrations in polarized epithelial cells or in non-polarized cells and a cooled CCD camera for documenting histologic slides. Core B also assists DDBTRCC investigators in preparation of intestine, liver, pancreas, and kidney for EM imaging and data interpretation.